Repairing a Keithley 130 multimeter

In this article we will going to attempt the repair of a Keithley 130 Multimeter (1980) that I’ve obtained as a deal sweetener while buying a resistor decade that was already a good deal, so basically for free.

This instrument is in a non-working state and all the labels on top are not a good start stating all the problems that the meter has.
The blackened display is already a clear problem with the crystals inside that have gone bad for external contamination.
Even if the multimeter is not very valuable for today standard, I’ve decided to attempt the repair anyway for thanks to my love for vintage instrumentation and for learning a history and electronics lesson.

Display Repair

There aren’t many information online about the Keithley 130 and the only schematic that I was able to find was hosted on the site.
The complete manual for the similar model 130A is available on the Tektronix site and is a nice reference.

Studying the manuals and the board of this instrument, opened in the meantime, I found out that the multimeter used an INTERSIL CHIP (the ITS80062) both for driving the display and the ADC.
After further investigating with the help of some interesting articles on the internet I found out that INTERSIL chip was a custom version for Keithley of the ICL7106, with a slighty different pinout but with very similar performance and working principle.
Kithley during that period was manufacturing some instruments with similar design to enter the newly formed market of relatively cheap digital multimeters.
Because of the very dead display and the fact that at first sight I wasent able to find other visible problems I decided to add to an order on DigiKey a screen with similar grafics but a slight different pinout and phisical dimensions
The screen selected is an Orient Display OD-358R (DigiKey 3444-OD-358R-ND).

Two days later I’ve tested the new display mounted on two breadboards with the display connector from the multimeter extended with a flat. After seeing the multimeter coming to life again I’ve executed a fast allignement to verify that was possible to get decently precise readings.
The pinout of the old display was extracted from the schematics and verified from observing with the right light the old display.

Verified that the only problem was the broken display I’ve decided to solder the new display to the pcb, but before I’ve cutted the long pin on the display as short as possible to still solder something on them.

I’ve also glued the display on the front protective plastic with two drops of hot glue.

Conclusion

After testing that no shorts have been created and with the case closed this repair work could be considered concluded, with the perfectly working multimeter aligned again for the final time.

Another multimeter for the lab and my collection, that will come in handy for on the move measure at the fairs to test some instruments before buying them.